1. Field of the Invention
The present invention relates in general to a monitor which is used as a video display unit of a computer system, and more particularly to a method for detecting and separating vertical and horizontal synchronous signals from the computer system.
2. Description of the Prior Art
Generally, the user monitors and checks the operation status of a computer system by means of a monitor. The computer system outputs a signal based on the current operation and the monitor displays the output signal from the computer system on its screen. The monitor utilizes vertical and horizontal synchronous signals to display the output signal from the computer system on the screen. For this reason, the computer system outputs the vertical and horizontal synchronous signals to the monitor together with data to be displayed on the screen of the monitor. The computer system outputs the vertical and horizontal synchronous signals in various manners.
For examples, the computer system may output the vertical and horizontal synchronous signals separately or as one composite synchronous signal wherein the vertical and horizontal synchronous signals are combined. Alternatively, the computer system may combine the vertical and horizontal synchronous signals on a green color signal and output the resultant one synchronous-on-green (SOG) signal.
The monitor must separate the vertical and horizontal synchronous signals from the computer system from each other to use them individually.
For this reason, the monitor has to check input forms of the vertical and horizontal synchronous signals from the computer system and separate the vertical and horizontal synchronous signals from each other in accordance with the checked result.
The vertical and horizontal synchronous signals from the computer system may be different in polarity.
For example, the polarities of the separated vertical and horizontal synchronous signals may be both positive or negative. Alternatively, one of the polarities of the separated vertical and horizontal synchronous signals may be positive and the other may be negative.
In the composite synchronous signal, the vertical and horizontal synchronous signals are the same in polarity. Namely, the polarities of the vertical and horizontal synchronous signals are both positive or negative. In the synchronous-on-green signal, the polarities of the vertical and horizontal synchronous signals are both positive.
In this connection, the monitor must use hardware to separate and change the polarities of the separated vertical and horizontal synchronous signals suitably for the use therein.
As a result, the exemplary monitor requires additional hardware design work for the synchronous signal separator, resulting in increases in manufacturing cost and size of a printed circuit board. For this reason, the manufactured goods are degraded in competitiveness.